1. Field of the Invention
This invention relates to apparatus for separating a solid or viscous liquid component from a mixture with a readily flowable liquid component of slightly greater specific gravity.
The invention was devised particularly for use in separating heavy contaminated viscous grease from treatment water used in wet blasting so that the water can be recirculated and the grease discarded.
2. Description of the Prior Art
Separation of this combination of heavy grease and water has hitherto caused considerable difficulty because the grease has a specific gravity only slightly less than the water and hence only just floats on the water. Where mechanical separation has previously been attempted by skimming settlement tanks for example, there has been a tendency for the grease to dip below the water surface as mechanical skimmers pass along the tank. The settlement tanks require to be quite large in view of the relatively slow separation of the grease layer from the water with which it is mixed so that, in addition to separation being inefficient, large areas of floor space have had to be given over to settlement tanks and the capital cost of providing separation means has been high.
Heavy viscous grease is difficult to remove from skimmers used in settlement tanks so that quite elaborate cleaning arrangements have been required to prevent excessive build-up on the skimmers.
In the field of sewage treatment, it is known, for example from British Pat. Nos. 390,989 of Mills, 483,582 of Hartley and 1,501,021 of Ecodyne Corporation, to skim a floating scum from the top of a settlement tank up an inclined ramp or "beach plate" and into a collection outlet. It is inherent in such apparatus that a quantity of the liquid in which the scum is floating is also discharged to the outlet. The only selectivity available is due to the difference in specific gravity between the liquid and the floating scum.
Such techniques are not directly applicable to the separation of heavy grease from water for example because the difference in specific gravity between the materials to be separated is so slight that an undesirably large proportion of the water would be discarded with the grease.
The present invention was devised in an attempt to overcome or reduce these disadvantages which are at present encountered in the separation of viscous greases from treatment water used in wet blasting. However, the invention is of more general applicability and may be used in other separation processes in which the solid or viscous liquid is to be separated from a mixture with a readily flowable liquid component of slightly greater specific gravity.